International Trade Barriers:

Free trade refers to the elimination of barriers to international trade. The most common barriers to trade are tariffs, quotas, and nontariff barriers.

Tariffs:

A tax imposed on imported goods and services. Tariffs are used to restrict trade, as they increase the price of imported goods and services, making them more expensive to consumers.

Quota:

In international trade, Quota is government-imposed limit on the quantity, or in exceptional cases the value, of the goods or services that may be exported or imported over a specified period of time.